Here's A Delicious Chess Problem That Had Me Scratching My Head For Hours

One of my favorite things to do for amusement is solve chess problems, wherein the player is given a scenario on the board and then asked how to go about checkmating the other side within X number of moves.

So I was pretty psyched yesterday when the eminent chess player and commenter Susan Polgar posted on her blog the following:

Black to move and checkmate in 3. Please no computer analysis. This is a very cool checkmate. Try to find it for yourself.

Now chess problems where you're asked to just mate in 3 moves aren't typically all that hard, so my curiosity was piqued by the fact that Polgar said not to use a computer. Obviously it couldn't be that simple if you're tempted to use a computer to solve a 3 move chess problem.

And it wasn't! In fact I spent the evening looking at it yesterday without getting it.

First of all, you should probably just stop reading on, and just try to solve it yourself.

Here's why it's so maddeningly hard.

Your first instinct is to lift the black rook on F8 and check the king on G4.

chessrookmove1 Susan Polgar

White's move here is obvious. White has to move the king, but it can't move the king to H3 because that would result in checkmate on the very next move by black sliding the rook over to H4. So the only real move for white is take the black pawn on G5 with the king.

This initially looks promising for black, since it would seem that the rook (now on F4) can be moved, exposing the white king to a new check from the bishop on E3. Unfortunately, white easily blocks this discovered check (that's what it's called when one piece checks the king by removing the piece in between them) by advancing the white pawn on F3 to F4. And then black is stymied.

So suddenly you start focusing on that pawn on F3, and how to prevent it from moving forward and thwarting your mate.

Aha! You can do that with the queen, threatening to move it to D1 at some point, pinning the white pawn against its own king, preventing it from moving.

chessmovewithqueen2 Susan Polgar

But actually this doesn't get you anywhere, because at this point the king is no longer on that diagonal (it's taken the black pawn), and so what looked like an interesting idea to prevent a pawn move is nonsense.

So then you start to think that maybe the first move isn't to check, and you think this is because you're super clever.

So you start thinking about attacking the H file, by moving your rook to H8.

rookmovesideways3 Susan Polgar

But it turns out this is loser too, since white can just move one of its pieces onto the H file, blocking any threat from the rook.

rookmovesidewaysq4 Susan Polgar

This is where things are really getting tough.

Finally, @ivanthek and @austerity_sucks got it on Twitter.

The key move is #2 and it's got nothing to do with the rook or the queen. It's the bishop, which you have to move to B6, for an eventual check on the king from D8 to G5.

chessolutionfinal Susan Polgar

As chess expert Mig Greengard put it on Twitter, this is a beautiful, lovely checkmate, filled with misdirection.

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